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The Future of Multimessenger Astronomy with Neutrinos at The The Future of Multimessenger Astronomy with Neutrinos at the South Pole IceCube and Future Observatories in the Ice Kael Hanson Director, Wisconsin IceCube Particle Astrophysics Center (WIPAC) University of Wisconsin – Madison 12th Latin American Symposium on High Energy Physics November 29, 2018 Classical Astronomy - The Visible Sky 2018 | 11 | 29 K. Hanson - XII SILAFAE 2 The Sky In Gamma Rays 2018 | 11 | 29 K. Hanson - XII SILAFAE 3 The Photon Sky at Ultrahigh Energies No – this is not me forgetting to add the slide content. Above several hundred trillion eV, photons don’t travel more than galactic distances. 2018 | 11 | 29 K. Hanson - XII SILAFAE 4 M87 – A Nearby Natural Particle Accelerator 2018 | 11 | 29 K. Hanson - XII SILAFAE 5 The Case for Multimessenger Astronomy Take all you are given High energy astrophysical acceleration sites are likely emitters of gammas, charged ions, and neutrinos. Each particle used as a messenger particle has it own strengths and weaknesses – we can push our knowledge deeper by combining them. Gamma rays: point back to sources and easily detectible but there is problem of interactions in dense sources or in transit over not-so-long distances. PeV and above constrained to intergalactic-scale distances. EM and hadronic production possible and often difficult to discriminate. Cosmic rays: and up to 1019 eV travel over cosmological distances. Not impossible but difficult to trace back to source due to deflection in GMF/IGMF. UHE detection requires large ground arrays. Neutrinos: point back to sources and offer pristine look even deep into compact objects; no horizon – a good thing overall but has implications in point-source searches; require large, expensive underground or underwater (ice) detector facilities; radio is however promising economical technique at UHE. 2018 | 11 | 29 K. Hanson - XII SILAFAE 6 Challenge / Opportunity: Cosmic Horizons Neutrinos are alone the only astronomical messengers capable of directly imaging the extreme energy sky. Photons interact with EBL and already at 100’s of TeV are limited to Mpc scales. Charged cosmic rays processed by galactic and inter-galactic magnetic fields as well as galactic diffusion: energy and angles at observation no longer follow source. 2018 | 11 | 29 K. Hanson - XII SILAFAE Slide 7 Atmospheric Neutrino “Backgrounds” Neutrinos are also produced in quantity by cosmic ray interactions in the Earth’s atmosphere: decaying mesons yield muons, ne, and nm (not nt however). These form a nearly irreducible background for astrophysical neutrinos (IceCube detects 1 every 5 minutes vs 1/week for astrophysical n). The handle is the energy: because mesons lose energy in the atmosphere the flux of atmospheric neutrinos is approx. power law with spectral index -3.7. 2018 | 11 | 29 K. Hanson - XII SILAFAE 8 IceCube Still the biggest TeV neutrino telescope The IceCube Collaboration includes > 300 researchers from 47 institutes in 12 countries. IceCube is one of the NSF’s large facilities (LIGO, LSST, … 2 dozen others). The Operations and Management of the facility is handled by WIPAC at UW- Madison. In addition to having a large science group, our center supports the technical aspects: computing, data storage, detector maintenance, … The IceCube Neutrino Observatory IceCube construction began in 2002 with design and procurement of the drill. The first string to be deployed was in Jan 2005. Over the next 6 season 85 more strings were deployed with the last string being “tied off” on December 17, 2010. Full 86 string data taking started May 2011. TPC: $279M USD - $40M non-US The South Pole site was chosen (A) Because there is a lot of ice; (B) Logistic support: 5 million lbs. of cargo were delivered and 77 person-years of effort on-ice it took to make IceCube. Everything was at that time airlifted inside LC-130 Hercules aircraft. 2018 | 11 | 29 K. Hanson - XII SILAFAE 12 The IceCube Digital Optical Module (DOM) Penetrator HV Divider Optical Communicatons / Timing LED Flasher . Large Area Photocathode 10” 10- . Comunications is digital at rate of Board stage Hamamatsu R7081-02 PMT 1 Mbit/s shared by 2 DOMs on a DOM single copper pair. Mainboard (QE 24% @ 420 nm); High QE . The DOMs each timestamp PMT variant (QE 35% @ 420 nm) used in pulses using a local XO. DeepCore DOMs Mu-metal Nevertheless, 1 ns time resolution grid . Low noise 500 Hz bkg count rate in- is achieved through automatic ice @ 0.25 pe threshold. clock synchronization protocol . Glass / Gel 0.5” thick Benthos Delay Board pressure housing rated to 10,000 Digitizer psi. Better transmission in 330 - 400 nm relative to AMANDA OM. IceCube adopted waveform readout Low radioactivity glass. of PMT pulses to deal with complex . Optical calibration Each DOM scattering of photons in ice. There calibrated ε(λ, T) in the lab to about are two digitizers: PMT RTV . 300 MSPS ASIC 14-bit effective gel 7%; in-situ flashers additionally permit in-ice optical measurements resolution but limited to ~500 ns Glass Pressure Housing . 40 MSPS pipelined ADC capture to 6.4 µs FPGA + ARM CPU SoC. 4k-hit deep Power supplied by 18 AWG Cu pair to surface (3.5 km). 96 V, memory buffer stores hits until readout Smart Sensor Power 3.75 W per channel (DOM) over 1 Mbit digital link to surface. 2018 | 11 | 29 K. Hanson - XII SILAFAE 13 Hot Water Drilling • 5 MW Drill power plant gives 195°F hot water in closed loop system. • 5500 gallons AN-8 jet fuel / hole • 30 man crew • 30 h drilling – 3 day cycle time • “Hole lifetime” – 24hr • DOM installation – 8 hr • Typical freezeback times > weeks • DOMs not operated in liquid under normal circumstances. Drilling improved over time. The first 2004-2005 hole took weeks to drill. A few years later the drill crew was able to get the time down to 50 h. By the end – 30 h was achieved with repeatable performance. 2018 | 11 | 29 K. Hanson - XII SILAFAE 14 Detecting Neutrinos in the Ice IceCube is “water” Cherenkov detector: we detect the charged ultrarelativistic secondaries which are produced in neutrino scattering in ice or detect CR muons and their stochastic secondaries. Ice is a good calorimetric medium: we can get 10% resolution on E (dE/dX for muons). Scattering and non-uniformity is problematic both for precision reconstruction and for simulation of the detector. Still we are able to obtain O(½) degree angular resolution for tracks. 2018 | 11 | 29 K. Hanson - XII SILAFAE 15 Ice The complex ice structure deposited over 100 k-yr contains much structure and is prominent challenge for IceCube: • Simulation of 1010 photons or more for high energy events now possible with GPU acceleration • Not only is there z structure, there is tilt and directional anisotropy! Ice properties measured with in-ice calibration sources: • 12 high brightness 400 nm LEDs per DOM – a few DOMs have different colors; • Handful of special calibrated sources; • Dedicated dust logging of boreholes – IceCube also contains a few glaciologists. 2018 | 11 | 29 K. Hanson - XII SILAFAE 18 It started with 2 muppets: Bert and Ernie Quite by accident, while looking for extremely high energy neutrinos from the GZK interacting protons, we found two events in the first year of full IC86 data that didn’t look like any background: they were clear cascade-like events which started inside the detector just like a neutrino should. And they had extremely high energy: 1.05 PeV and 1.15 PeV, each had nearly 100,000 detected photo-electrons! Now that we had seen real, unmistakable signal events with our “eyes”, we knew how to proceeed: 2018 | 11 | 29 K. Hanson - XII SILAFAE 19 High-Energy Starting Event (HESE) Analysis Strategy: focus on high-energy events (2 > PeV events in 1 year, either we got really lucky or the ice is full of them). The very simple cut developed (it is now running in real time at Pole) is this: • Qtot > 6000 p.e. : this will setup an energy threshold of approx. 30 TeV, but, again, there should be many events out there based on the two observations; • Use part of IceCube’s outer shell as a veto. It’s OK if hits occur in the veto as the particle exits (PC muons will do this) but not OK if the first hits occur in the veto region. • It is also possible to use data to check the veto performance The HESE analysis was then sensitive to all flavors above about 60 TeV (muons are penalized slightly because some energy escapes); background could be estimated from data. The effective volume of the search was 400 Mton – about 40% efficient. 2018 | 11 | 29 K. Hanson - XII SILAFAE 20 HESE 6-year Results 2018 | 11 | 29 K. Hanson - XII SILAFAE 21 TXS 0506+056 First Observation of Astrophysical Source in EM and Neutrinos I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhäuser Gate. All those moments will be lost in time, like tears in rain … -- Roy Batty (Rutger Hauer) Blade Runner (1982) The IceCube Realtime System • IceCube operates largest data center on continent • Digital data packets from sensors sent to surface and processed by software trigger and readout system (IceCube DAQ) – 3 kHz trigger rate (mostly cosmic ray muons from above) yields about 10 MB/sec written to disk with ~ 5 sec latency. • Online compute farm performs event reconstructions. • High significance events sent via Iridium satellite link to Northern Hemisphere where automated GCN alerts sent out. • IceCube has been sending RT alerts several years but high- energy tracks sent only since Spring 2016 – about 10/yr. • On 22 Sept 2017 at 20:54:30.43 UTC alert IC170922 issued • 43 seconds elapsed between event in ice and GCN alert dissemination on network.
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